Installation and Use
We benchmarked the Seasonic X series 650W in a newer system after another PSU fried the motherboard and processor in my standard testing rig. This newer system has a ASUS P6T Deluxe motherboard with a Intel Core i7 965 @ 3.2 ghz, 12 GB DDR3 memory, ATI Radeon 4870 x2, two 256gb ssds, two 1TB SATA drives, and a Blu-ray drive in a case with a pair of fans.

At idle, the Seasonic X series 650W pulled 3.26V, 4.99V, 12.26V on the 3.3V, 5V, and 12V rails, respectively, and pulled around 3.23V, 4.94V, 12.1V at load.

We used OCCT Perestroika to do load testing. Here are the output graphs comparing the voltages of the Seasonic X series 650W with my trusty Antec Truepower 1000W, the PSU I know the best. The X series results are on the left and the Truepower 1000W results are on the right.

This rig tends to pull a lot of power from the 3.3V rail, so it’s no surprise that that rail undervolted throughout the tests. The ripple wasn’t bad–only .92%. It was fairly stable, though, jumping only every now and then.

The 5V rail was almost entirely stable. There were a few drops during the bulk of the testing, but it otherwise held its own. The ripple was fine, and the voltage was well within limits.

The 12V rail dropped more than .1V during tests, but overvolted by quite a bit. A similar effect can be seen with the higher power Antec Truepower 1000W. There’s a heavy pull from the video card in this rig.The spikes were minimal, and by only .05V.

The noise level was nothing special. The X series ramps up the fan after 20% load, keeping it silent when the the PSU isn’t under any stress. Given the stress on this PSU from the Core i7 and dual 4870s, it was in the middle stage, where the fan was on but blowing just a gentle breeze. During the tests however, the PSU fan kicked in and kept the X series cool.